linux-cve-announce - CVE-2022-50227: KVM: x86/xen: Initialize Xen timer only once

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Message-ID: <2025061849-CVE-2022-50227-890e@gregkh>
Date: Wed, 18 Jun 2025 13:04:52 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50227: KVM: x86/xen: Initialize Xen timer only once

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

KVM: x86/xen: Initialize Xen timer only once

Add a check for existing xen timers before initializing a new one.

Currently kvm_xen_init_timer() is called on every
KVM_XEN_VCPU_ATTR_TYPE_TIMER, which is causing the following ODEBUG
crash when vcpu->arch.xen.timer is already set.

ODEBUG: init active (active state 0)
object type: hrtimer hint: xen_timer_callbac0
RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:502
Call Trace:
__debug_object_init
debug_hrtimer_init
debug_init
hrtimer_init
kvm_xen_init_timer
kvm_xen_vcpu_set_attr
kvm_arch_vcpu_ioctl
kvm_vcpu_ioctl
vfs_ioctl

The Linux kernel CVE team has assigned CVE-2022-50227 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.19 with commit 536395260582be7443b0b35b0bbb89ffe3947f62 and fixed in 5.19.2 with commit 9a9b5771e930f408c3419799000f76a9abaf2278
	Issue introduced in 5.19 with commit 536395260582be7443b0b35b0bbb89ffe3947f62 and fixed in 6.0 with commit af735db31285fa699384c649be72a9f32ecbb665

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-50227
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	arch/x86/kvm/xen.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/9a9b5771e930f408c3419799000f76a9abaf2278
	https://git.kernel.org/stable/c/af735db31285fa699384c649be72a9f32ecbb665